I am not entirely sure what happened. My coop is open for free range until it gets cold enough that guinea roosts inside. When that happens, he is securely shut in at dusk. He was still roosting in the tree so as of yesterday he moved about as he would. My coop is half enclosed, half 'open' with normal-sized doors on each end for my entry & a little doggie-style door for guinea's entry into the enclosed half, passing thru the big door in the 'open' half & into the enclosed half for roosting. He wasn't using the coop yet this season but did go in from time to time to use his little dirt bath areas he had made.
I lost a guinea last year to a fox. The fox took him to the back of our five acre property. Yesterday, I found guinea inside the 'open' half of the coop up next to the wall of where the enclosed half starts. Whatever got him tried to drag him under the enclosed half flooring. He certainly was too big for whatever it was to be successful. A fox would not have been able to fit under there either.
I put a motion sensor out there in the open half of the coop and actually it is going off as I type this. I don't have an extension cord for the spotlight I bought so maybe this animal too will go in my live trap. We'll see in the morning.
BTW, I only had two guineas so safety is not a concern at this point.